Battery stack configuration in a multi-battery supply system

ABSTRACT

A reconfigurable multi-battery pack system for inclusion in a hand held device for more efficiently energizing battery powered operation of both a buck DC-DC converter and a boost DC-DC converter included in the device. Also disclosed is a power management circuit that autonomously:
         1. connects the batteries in parallel during battery recharging; and   2. connects at least two (2) of the batteries in series when the batteries are not being recharged and are energizing operation of the DC-DC converters.

BACKGROUND

Technical Field

The present disclosure relates generally to electrical power managementfor hand held equipment, particularly managing electrical power suppliedfrom several batteries.

Background Art

Tablet computers such as Apple Corporation's iPad®, Amazon's Kindle Fireand Barnes & Noble's Nook include a power management integrated circuit(“PMIC”) for converting electrical power at a battery's voltage to otherrequired voltages. Usually, a tablet computer's PMIC provides electricalpower at two (2) different voltages, i.e.:

-   -   1. a low voltage in the range of 1.8v or lower for energizing        operation of the tablet computer microprocessor (“μP”) and        perhaps other integrated circuits (“ICs”) included therein; and    -   2. a higher voltage in the range of 20-40v for energizing        operation of the tablet computer's display.

As illustrated schematically in a block diagram FIG. 1A, a tabletcomputer frequently has battery system 22 that includes three (3)individual Li-Ion battery packs 24. In the illustration of FIG. 1A, abuck converter circuit 26 converts the voltage of direct currentelectrical power from the battery system 22, e.g. 4v, to a lower voltagedirect current electrical power, e.g. 1.8v. Similarly, a boost convertercircuit 28 converts the voltage of direct current electrical power fromthe battery system 22 to a higher voltage direct current electricalpower, e.g. 24 or 36v.

The configuration of the battery system 42 and the buck and boostconverter circuits 26, 28 depicted in FIG. 1A uses a single batteryvoltage connected respectively to power inputs 32 of the buck and boostconverter circuits 26, 28 for generating both 1.8 v and 36v electricalpower. The parallel arrangement of the battery packs 24 depicted in FIG.1A is simple though it requires a high current for charging the batterypacks 24 in parallel. However, the configuration depicted in FIG. 1A isnot optimized for efficient power conversion by a PMIC. The depictedconfiguration favors efficient electrical power conversion by the buckconverter circuit 26 but sacrifices electrical power conversionefficiency by the boost converter circuit 28.

As depicted in FIG. 1A, a tablet computer also usually includes abattery charger circuit 36 for supplying electrical power for rechargingthe battery packs 24. In conventional tablet computers the batterycharger circuit 36 includes an input terminal 38 that receiveselectrical power from an external power source usually at approximately5.0v.

FIG. 1B illustrates in greater detail a power management circuitincluded in a typical hand held device 48 such as a tablet computer.Such a hand held device may include several individual buck convertercircuits 26 a, 26 b, 26 c that respectively supply electrical power at1.0v, 3.3v and 2.5v to a microprocessor 52, a WI-FI transceiver 54, anda RAM memory 56. The boost converter circuit 28 included in the handheld device 48 supplies electrical power to a display 58 at perhaps24.0v.

in addition to the battery charger circuit 36, the hand held device 48also includes a detector circuit 62 that senses connection of anelectrical power source such as an AD/DC adaptor 64 to the inputterminal 38 of the hand held device 48. The detector circuit 62 respondsto connecting a AD/DC adaptor 64 to the input terminal 38 by supplying asignal for closing a normally open switch 66 located between the batterycharger circuit 36 and the battery system 22 so a recharging currentflows to the battery packs 24.

U.S. Pat. No. 6,504,340 entitled “Hands-free Kit for Mobile Phones UsingSolar Cell” that issued Jan. 7, 2003, on a patent application filed bySea Sun Lee (“the '340 patent”) discloses, similar to the illustrationof FIG. 1A, a configuration for recharging one or more batteries. Duringrecharging, the batteries are connected in parallel with each other andwith a solar cell that provides a low voltage source of chargingelectrical power. When supplying electrical power for energizing theoperation of a disclosed “hands-free kit,” the rechargeable batteriesbecome connected in series. While the batteries are being charged inparallel, the '340 patent's “hands-free kit” is inoperable.

Published United States Patent Application No. 2012/0293128 entitled“Battery Pack” filed by Bongyoung Kim and Kiho Shin that was publishedNov. 22, 2012, similarly discloses connecting a plurality of batteries:

-   -   1. in parallel during high-efficiency charging that reduces        overall charging time; and    -   2. in series when providing high-output voltage for energizing        operation of a hand held electronic device such as a cellular        phone, a notebook computer, a camcorder, or a personal digital        assistant (PDA).

BRIEF SUMMARY

The present disclosure provides a multi-battery pack system that whenthe batteries are not being recharqred reconfigures the batteries formore efficiently energizing operation of a hand held device such as atablet computer.

Briefly, disclosed are a method for reconfiguring a multi-battery packsystem for more efficiently energizing a hand held device's operation,and a power management circuit for autonomously reconfiguring a handheld device's multi-battery pack system so the device operates moreefficiently.

The disclosed battery reconfiguration method more efficiently energizesoperation of the hand held device that includes:

-   -   1. at least two (2) rechargeable batteries;    -   2. a buck DC-DC converter; and    -   3. a boost DC-DC converter.        Each of the DC-DC converters respectively has a power input that        receives electrical power for energizing the converters'        operation. The method includes connecting the batteries in        series with:    -   1. the series connected batteries being connected to the power        input of the boost DC-DC converter for energizing the operation        thereof; and    -   2. one of the series connected batteries being connected to the        power input of the buck DC-DC converter for energizing the        operation thereof.        Configured in this way the hand held device's boost DC-DC        converter operates more efficiently in comparison with operation        thereof being energized by the batteries connected in parallel.

Also disclosed is a battery powerable device that includes:

-   -   1. at least two (2) rechargeable batteries;    -   2. a buck DC-DC converter; and    -   3. a boost DC-DC converter.        Each of the DC-DC converters respectively has a power input that        receives electrical power for energizing the converters'        operation. The battery powerable device includes a power        management circuit that, when the device is connected to a        electrical power source for recharging the batteries, configures        the batteries in parallel with the parallel connected batteries        being connected to the power inputs of the buck and boost DC-DC        converters for energizing their operation. When the device is        not connected to an electrical power source for recharging the        batteries, the power management circuit connects at least        two (2) batteries in series with:    -   1. the series connected batteries being connected to the power        input of the boost DC-DC converter for energizing the operation        thereof; and    -   2. one of the series connected batteries being connected to the        power input of the buck DC-DC converter for energizing the        operation thereof.        By configuring the batteries in this way the power management        circuit advantageously makes the hand held device's boost DC-DC        converter operate more efficiently in comparison with operation        thereof being energized by the batteries connected in parallel.

These and other features, objects and advantages will be understood orapparent to those of ordinary skill in the art from the followingdetailed description of the preferred embodiment as illustrated in thevarious drawing figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1a is a block diagram schematically depicting a conventionalconfiguration for supplying electrical power within a hand held devicesuch as a tablet computer that includes a battery system, a batterycharger circuit, a buck converter circuit and a boost converter circuit;

FIG. 1B is a block diagram schematically depicting in greater detail apower management circuit included in a typical hand held device such asa tablet computer;

FIG. 2 is a block diagram depicting a reconfiguration of the batterysystem, the buck converter circuit and the boost converter circuitdepicted in FIG. 1A for more efficiently energizing operation of a handheld device such as a tablet computer;

FIG. 3a is a block diagram depicting the reconfigured battery system,the buck converter circuit and the boost converter circuit depicted inFIG. 2 further equipped with a battery charger circuit that differs fromthe battery charger circuit depicted in FIG. 1A in that FIG. 3A'sbattery charger circuit is adapted for providing recharging current attwo (2) different voltages for recharging batteries configured asdepicted in FIG. 2;

FIG. 3B is a block diagram depicting the reconfigured battery system,the buck converter circuit and the boost converter circuit depicted inFIG. 2 that is:

-   -   a. equipped with the battery charger circuit depicted in FIG.        1A; and    -   b. also further equipped with a pair of switches that        dynamically rearrange battery connections from that for more        efficient operation depicted in FIG. 2 into that for battery        recharging depicted in FIG. 1A;

FIG. 3C is a block diagram depicting the reconfigured battery system,the buck converter circuit and the boost converter circuit depicted inFIG. 3B with the pair of switches arranged for more efficientlyenergizing operation of a hand held device such as a tablet computerwhen the batteries are not being recharged; and

FIG. 4 is a block diagram schematically depicting in greater detail apower management circuit in accordance with the present disclosure:

-   -   a. when included in a typical hand held device of the type        depicted in FIG. 1B; and    -   b. more efficiently energizing the hand held device's operation        when the batteries are not being recharged.

DETAILED DESCRIPTION

FIG. 2 depicts a reconfiguration of the battery packs 24, the buckconverter circuit 26 and the boost converter circuit 28 for moreefficiently energizing operation of a hand held device such as a tabletcomputer. In the illustration of FIG. 2, two (2) of the battery packs 24connect in parallel for supplying electricity to the power input 32 ofthe buck converter circuit 26 while the third battery pack 24 connectsin series with the parallel connected pair of battery packs 24 forsupplying electricity to the power input 32 of the boost convertercircuit 28.

Those skilled in the art understand that the efficiency of a boostconverter circuit, i.e. a converter circuit used for increasing voltage,is directly proportional to the input voltage. Conversely, those skilledin the art also know that the efficiency of a buck converter circuit,i.e. a converter circuit used for reducing voltage, is inverselyproportional to the input voltage. Consequently, a buck convertercircuit such as the buck converter circuit 26 receiving a 2.5v-3.0vsupply voltage at the power input 32 thereof achieves high efficiencyfor producing 1.8v DC electrical output power. Conversely, a boostconverter circuit such as the boost converter circuit 28 receiving a15.0v-20.0v supply voltage at the power input 32 thereof achieves highefficiency for producing 36v DC electrical output power.

Consequently, the two (2) battery packs 24 supply electrical power tothe power input 32 of the buck converter circuit 26 near an optimumvoltage, i.e. 4.0v. However, supplying this same electrical power at4.0v to the power input 32 of the boost converter circuit 28 as depictedin FIG. 1 causes its operation for producing 36v DC electrical outputpower to be very inefficient. Connecting the third battery pack 24 inseries with the pair of parallel connected battery packs 24 as depictedin FIG. 2 doubles to 8.0v the voltage of electrical power supplied tothe power input 32 for energizing operation of the boost convertercircuit 28. Doubling the voltage energizing operation of the boostconverter circuit 28 in this way reduces power dissipation within theboost converter circuit 28 by at least one-half in comparison withenergizing the boost converter circuit with 4.0v electrical power.

If in addition to producing electrical energy at the same voltage, e.g.4.0v, the battery packs 24 all store essentially the same amount ofelectrical energy, the configuration depicted in FIG. 2 matches atypical tablet computer's electrical power loads to the storage capacityof the battery packs 24. Typically a tablet computer imposes a 20 W loadon the buck converter circuit 26 and a 6 W load on the boost convertercircuit 28. That is, connecting two (2) battery packs 24 in parallel forsupplying electrical energy to the power input 32 of the buck convertercircuit 26 appropriately matches the electrical storage capacity ofthose battery packs 24 to the electrical power load supplied by the buckconverter circuit 26.

There exist variations of the battery system 22 and the buck and boostconverter circuits 26, 28 configurations depicted in FIG. 2 that alsoreduce electrical power dissipation in the boost converter circuit 28.One such alternative configuration depicted in FIG. 3A employs a staticor fixed configuration for the battery packs 24 and the buck and boostconverter circuits 26, 28 depicted in FIG. 2 while adding thereto abattery charger circuit 36′ having electrical characteristics thatdiffer from the battery charger circuit 36 depicted in FIG. 1.Specifically, the battery charger circuit 36 depicted in FIG. 3Aincludes a lower charging voltage output 42 for supplying rechargingcurrent directly to the pair of battery packs 24 connected in parallel.The battery charger circuit 36′ also includes a higher charging voltageoutput 44 for supplying recharging current to the battery pack 24 thatconnects in series with the parallel connected pair of battery packs 24.Note that recharging current supplied from the higher charging voltageoutput 44 recharges not only the battery pack 24 connected to the powerinput 32 of the boost converter circuit 28 but also recharges the pairof parallel connected battery packs 24. Note further that electricalpower supplied to the input terminal 38′ of the battery charger circuit36′ must have a higher voltage than that supplied to the input terminal38 of the battery charger circuit 36 depicted in FIG. 1, e.g. 10v forthe configuration depicted in FIG. 3A.

FIG. 3B depicts yet another configuration for the battery system 22 andthe buck and boost converter circuits 26, 28 that differs from thatdepicted in FIG. 2 and that similarly reduces electrical powerdissipation in the boost converter circuit 28 when operation of the handheld device is energized solely by the battery packs 24. Theconfiguration depicted in FIG. 3B differs from the configurationdepicted in FIG. 3A:

-   -   1. by using the same battery charger circuit 36 as that depicted        in FIG. 1; and    -   2. by adding a pair of synchronously operated switches 72 a, 72        b to the configuration depicted in FIG. 2 with the switches        connected respectively to terminals of the battery pack 24 that        in the illustration of FIG. 2 connects to the power input 32 of        the boost converter circuit 28.        Specifically, FIG. 3B depict an arrangement of the switches 72        a, 72 b in which the battery pack 24 that connects to the power        input 32 of the boost converter circuit 28 also connects in        parallel with the other two (2) battery packs 24 while the input        terminal 38 of the battery charger circuit 36 receives        electrical power from an external source at approximately 5.0v        for recharging all three (3) battery packs 24. Consequently,        from a circuit topology perspective the configuration of the        battery system 22 and the buck and boost converter circuits 26,        28 depicted in FIG. 3 is the same as that depicted in FIG. 1        with electrical power at 4.0v energizing operation of both the        buck and boast converter circuits 26, 28. While as described        above this arrangement of the switches 72 a, 72 b reduces power        conversion efficiency of the boost converter circuit 28 in        comparison with the configuration depicted in FIG. 2, from a        practical perspective the battery charger circuit 36 effectively        provides a source of unlimited electrical power so lower        electrical conversion efficiency of the boost converter circuit        28 is irrelevant to a hand held device's operation.

FIG. 3C illustrates the configuration of FIG. 3B when:

-   -   1. the input terminal 38 of the battery charger circuit 36        receives no electrical power from an external source for        recharging the battery packs 24; and    -   2. operation of a hand held device is being energized solely by        the battery system 22 with:        -   a. only a single battery pack 24 connected to the power            input 32 of the boost converter circuit 28; and        -   b. the switches 72 a, 72 b connect that battery pack 24 to            the parallel connected pair of battery packs 24 supplying            electrical energy to the power input 32 of the buck            converter circuit 26.            From a circuit topology perspective the configuration of the            battery system 22 and the buck and boost converter circuits            26, 28 depicted in FIG. 3C is the same as that depicted in            FIG. 2 with electrical power at 8.0v energizing operation of            the boost converter circuit 28. Since this arrangement of            the switches 72 a, 72 b configures the battery system 22 and            the buck and boost converter circuits 26, 28 the same as            depicted in FIG. 2, electrical power dissipation in the            boost converter circuit 28 only one-half of that exhibited            by the configuration depicted in FIG. 1.

The block diagram of FIG. 4 schematically illustrates one way in whichthe present disclosure may be implemented in the typical hand helddevice 48 depicted in FIG. 1b for more efficiently energizing operationthereof. The hand held device 48′ depicted in FIG. 4 differs from thatdepicted in FIG. 1b by including the pair of synchronously operatedswitches 72 a, 72 b similar to those depicted in FIGS. 3B and 3C. Theconfiguration of the switches 72 a, 72 b depicted in FIG. 4, whilefunctionally equivalent to that depicted in FIGS. 3A and 3B, usesslightly different connections.

During battery recharging, similar to the illustration of FIG. 3B, theswitch 72 a depicted in FIG. 4 is closed thereby connecting together thepositive (+) terminals of all battery packs 24 while the switch 72 bdepicted in FIG. 4 connects the negative (−) terminal of one of thebattery packs 24 to circuit ground. Configured in this way theindividual buck converter circuits 26 a, 26 b, 26 c and the boostconverter circuit 28 all receive identically the same lower voltageelectrical power from the battery charger circuit 36 that isconcurrently being supplied for recharging the battery packs 24.

When the battery packs 24 are not being recharged, rather than depictedin FIG. 3C the switch 72 a connecting the negative (−) terminal of oneof the battery packs 24 to the positive (+) terminal of the remainingbattery packs 24, in the illustration of FIG. 4 the switch 72 b connectsthe negative (−) terminal of one of the battery packs 24 to the positive(+) terminal of the remaining battery packs 24. Either of thealternative configurations illustrated in FIGS. 3C and 4, doubles thevoltage being supplied to the boost converter circuit 28 in comparisonwith the voltage being supplied to the buck converter circuits 26 a, 26b, 26 c.

Finally, the detector circuit 62′ included in the hand held device 48′,in addition to responding to connection of a AD/DC adaptor 64 to theinput terminal 38 by supplying a signal for closing the normally openswitch 66, also supplies a pair of signals for respectively:

-   -   1. closing the switch 72 a; and    -   2. changing the switch 72 b from connecting;        -   a. the negative (−) terminal of one of the battery packs 24            to the positive (+) terminal of the remaining battery packs            24; to        -   b. the negative (−) terminal of the battery pack 24 to            circuit ground.            Thus the additional pair of signals supplied by detector            circuit 62′ reconfigures the battery packs 24 from a            configuration which more efficiently energizes operation of            the hand held device 48′ to a configuration for recharging            the battery packs 24 in parallel, and conversely.

Although the present invention has been described in terms of thepresently preferred embodiment, it is to be understood that suchdisclosure is purely illustrative and is not to be interpreted aslimiting. Consequently, without departing from the spirit and scope ofthe disclosure, various alterations, modifications, and/or alternativeapplications will, no doubt, be suggested to those skilled in the artafter having read the preceding disclosure. Accordingly, it is intendedthat the following claims be interpreted as encompassing allalterations, modifications, or alternative applications as fall withinthe true spirit and scope of the disclosure including equivalentsthereof. In effecting the preceding intent, the following claims shall:

-   -   1. not invoke paragraph 6 of 35 U.S.C. §112 as it exists on the        date of filing hereof unless the phrase “means for” appears        expressly in the claim's text;    -   2. omit all elements, steps, or functions not expressly        appearing therein unless the element, step or function is        expressly described as “essential” or “critical;”    -   3. not be limited by any other aspect of the present disclosure        which does not appear explicitly in the claim's text unless the        element, step or function is expressly described as “essential”        or “critical;” and    -   4. when including the transition word “comprises” or        “comprising” or any variation thereof, encompass a non-exclusive        inclusion, such that a claim which encompasses a process,        method, article, or apparatus that comprises a list of steps or        elements includes not only those steps or elements but may        include other steps or elements not expressly or inherently        included in the claim's text.

1. A method for energizing operation of a device includes at least two(2) rechargeable batteries, the device also including both at least one(1) buck DC-DC converter and at least one (1) boost DC-DC converter witheach DC-DC converter respectively having a power input that receiveselectrical power for energizing DC-DC converter operation, the methodcomprising the step of connecting the batteries to series with: a. theseries connected batteries being connected to the power input of theboost DC-DC converter for energizing the operation thereof; and b. oneof the series connected batteries being connected to the power input ofthe buck DC-DC converter for energizing the operation thereof, wherebyduring battery powered operation of the device the boost DC-DC converteroperates more efficiently in comparison with operation thereof beingenergized by the batteries connected in parallel.
 2. The method of claim1, wherein the device further includes a batter charger circuit thatreceives electrical power from a electrical power source that is locatedoutside the device, the battery charger circuit having both a lowercharging voltage output and a higher charging voltage output forsupplying individual recharging electrical currents to the batterieswhen the battery charger circuit is connected to the electrical powersource, the method comprising the additional steps of: c. connecting thehigher charging voltage output of the battery charger circuit to theseries connected battery that connects to the power input of the boostDC-DC converter; and d. connecting the lower charging voltage output ofthe battery charger circuit to the battery that connects to the powerinput of the buck DC-DC converter.
 3. The method of claim 1 wherein thedevice further includes battery charger circuit that receives electricalpower from a electrical power source that is located outside the device,the battery charger circuit having only a single lower charging voltageoutput for supplying recharging electrical current to batteries when thebattery charger circuit is connected to the electrical power source, themethod comprising the additional steps of: when the battery chargercircuit is connected to the electrical power source, connecting thebatteries in parallel and the parallel connected batteries beingconnected to the power inputs of both the buck DC-DC converter and boostDC-DC converter; and b. when the battery charger circuit is notconnected to the electrical power source, connecting the batteries inseries with: i. the series connected batteries being connected to thepower input of the boost DC-DC converter; and ii. One of the seriesconnected batteries being connected to the power input of the buck DC-DCconverter.
 4. (canceled)
 5. (canceled)